beated the game yesterday for the first time
(SPOILER)

And you are basing the possible second-language mistake solely on his User Name? Kudos to you good sir.

No, that's just a snippy remark about another interpretation of the username.

The possibility of a second-language mistake is just from keeping a sliver of doubt for those who are not so fortunate to have grown up with such a terrible language. Or maybe I subconsciously noticed that it was used as a past-tense verb, and that "beat" is also a present-tense verb, so by general rule, it might seem to a non-native speaker that the past tense is "beated"; on the other hand, "beat" is a pretty common word in both tenses, so a native speaker probably would've encountered it enough not to make that mistake.

But no, I didn't take the name into account at all when considering the likelihood of him being a non-native speaker.

He's like the most helpful person on this board unless things have drastically changed.

Oh yeah, we forgot to answer OP's question:

Are there any story scenes in this dungeon or just fights?

There's a scene and battle at the End.

Edit: On the other hand, "his being" and "him being" are less common...